Heretofore, there is known a technique of detecting a license plate from an image captured by using a digital camera or the like. In the detection of a license plate, multiple rectangles for license-plate-region candidates are detected from an input image. A License-plate-region candidate is selected from the multiple candidates based on character recognition results and information about the rectangles for the license-plate-region candidates.
For example, Japanese Laid-open Patent Publication No. 2008-217347 and Japanese Laid-open Patent Publication No. 2003-331384 disclose examples of the related art.